The PET line was Commodore's first computer line after purchasing MOS Technologies, the primary design of the computer (as well as its microprocessor, the 6502) was by Chuck Peddle. The line was labeled in series' the first series, the 2001 series, the European 3000 series, and the modern 4000 and 8000 series, and the final single unit 9000 series which is the SuperPET. In Europe due to trademark problems with Phillips Electronics commodore had to drop the PET name early and used the CBM (Commodore Business Machine) abbriviation instead - in the U.S. CBM was used to on the 'business class' PETs and PET/CBM disk drives and printers.

This unit was usually a 2001 series PET which was re-labeled with “Teacher's PET, Donated by Commodore Business Machines”

The story behind these in many US schools (at Least in California, where I know of it) Commodore had a promotion where if schools bought 2 PETs the third would be 'donated by Commodore. This was a tax write-off and marketing plan for the company similar to Apple's promotion of “an Apple for every school”.